The state department announced on Wednesday that North Korea will also allow international inspectors to verify activities at its main reactor.
In exchange, the Obama administration will ship 240,000 metric tons of food aid to the impoverished nation.
Still, it's unclear when the moratorium will begin, when inspectors will be allowed back in or when international negotiations will resume.
Secretary of State Hillary Rodham Clinton called the developments a "modest first step," but said it also serves as "a reminder that the world is transforming around us."
Since 2006, North Korea has tested missiles, staged two nuclear tests and unveiled a uranium enrichment program that could give it a second route to manufacture nuclear weapons.
Clinton said the United States will meet with North Korea to finalize details for the proposed food aid, referring to it as "nutritional assistance." She said intensive monitoring of the aid would be required.
North Korea appealed for the aid a year ago to alleviate chronic food shortages.
A spokesman from North Korea's Foreign Ministry said in a statement carried by the state-run news agency that the North agreed to the nuclear moratoriums and the allowance of U.N. inspectors "with a view to maintaining positive atmosphere" for the U.S.-North Korea talks.
The U.S. still has nearly 30,000 troops based in South Korea, a legacy of the 1950-53 Korean War, that ended in an armistice rather than a peace treaty.
Wednesday's announcement follows talks in Beijing last week between U.S. and North Korean negotiators, the first since negotiations were suspended after Kim Jong Il's death in December from a heart attack.
Before Kim's death, the U.S. and North Korea were close to such an agreement, which appears to meets U.S. preconditions for restarting the six-nation talks suspended three years ago. The talks also include China, Japan, Russia and South Korea.
North Korea's willingness to agree to the moratoriums and allow in U.N. inspectors is a major sign of the country's intentions in the early days of the ruler Kim Jong Un, the elder Kim's youngest son, who is believed to be in his late 20s.
The Associated Press contributed to this report.